We propose to investigate the metabolic properties of capillaries isolated from bovine brain and retina. The microvessels are prepared from disaggregated tissue by density flotation and glass bead filtration. Studies will be performed on endothelial cells in culture as well as intact capillaries in suspension. We will determine the pattern of glucose and fatty acid metabolism by these cells. In addition, the response of the cells to various hormones that may regulate their metabolic activity will be determined. We will search for the differences in function that are responsible for the susceptibility of retinal capillaries and the resistance of brain capillaries to injury in diabetes mellitus.